Host-Sensitized Luminescence Properties in CaNb2O6In3+ (Ln3+ = Eu3+/Tb3+/Dy3+/Sm3+) Phosphors with Abundant Colors

A series of Ln(3+) (Ln(3+) = Eu3+/Tb3+/Dy3+/Sm3+) ion doped CaNb2O6 (CNO) phosphors have been prepared via the conventional high-temperature solid-state reaction route. The X-ray diffraction (XRD) and structure refinement, diffuse reflection, photoluminescence (PL), and fluorescent decay curves were used to characterize the as-prepared samples. Under UV radiation, the CNO host present a broad emission band from about 355 to 605 nm centered around 460 nm originating from the NbO6 octahedral groups, which has spectral overlaps with the excitation of f-f transitions of Eu3+/Tb3+/Dy3+/Sm3+ in CNO:Eu3+/Tb3+/Dy3+/Sm3+ samples. They show both host emission and respective emission lines derived from the characteristic f-f transitions of activators, which present different emission colors owing to the energy transfer from the NbO6 group in the host to Eu3+/Tb3+/Dy3+/Sm3+ with increasing activator concentrations. The decreases of decay lifetimes of host emissions in CNO:Eu3+/Tb3+/Dy3+/Sm3+ demonstrate the energy transfer from the hosts to Eu3+/Tb3+/Dy3+/Sm3+. The energy transfer mechanisms in CNO:Eu3+/Tb3+/Dy3+ phosphors have been determined to be a resonant type via dipole-dipole mechanisms. For CNO:Sm3+, the metal-metal charge transfer transition (MMCT) might contribute to the different variations of decay lifetimes and emission intensity from CNO:Eu3+/Tb3+/Dy3+ samples. The best quantum efficiency is 71.2% for CNO:0.01/0.02Dy(3+). The PL properties of as-prepared materials indicate the promising application in UV-pumped white-emitting lighting diodes field.